Theories of the Universe: The Standard Model
The Standard Model
Given the state of cosmology today it's probably a good idea to spend the rest of this section providing you with an understanding of where the conventional theories are taking us. The standard model in cosmology is the big bang. And while plasma cosmology is a potential alternative, it'll still be a while before it finds more adherents. So let's continue with some aspects of the big bang that we haven't covered yet. The focus of this discussion revolves around the three possible scenarios of how the universe will end. Two of these can be summarized as follows:
The second law of thermodynamics simply states that things wear out. But to be a little more scientific, it is one of three fundamental laws in the study of heat. It expresses the physical law that heat cannot flow from a cold object to a hotter object of its own volition. For example, an ice cube in a cup of warm water melts as the heat flows into it from the water, ending up with a cup of water slightly cooler than the one we started with. But you never see ice cubes spontaneously forming in cups of water; they can only be formed by pumping the heat out of the water, which is what happens in your freezer. The process can only go in one direction. It's not reversible.
- The big crunch is the mirror reverse of the big bang. This would happen if the amount of gravitational force in the universe were strong enough to bring the currently expanding universe to an end. The universe would then stop expanding and eventually collapse back in on itself.
- The big chill is the opposite of the big crunch. In this scenario the universe would continue to expand forever. There is not enough gravitational force to stop the expansion, and eventually all of the stars and galaxies would exhaust their supply of energy and the universe would cool down and there would be no heat left. Everything would be cold, cold, cold. Brrhhhh!
The study of what goes on inside systems is called general systems theory. It's a fascinating area of study that examines the rules governing closed and open systems, which are the two types of possible systems. These systems are found all around us in nature, society, the Earth, the solar system, the universe, and even ourselves. We've learned a lot about the interdependence of systems and how the imbalance in one can affect the balance of others. A good example of this is the impact we have had on our environment. What do you think is out of balance in us, which has in turn put the environment out of balance?
I think you can see from the preceding summary that the most important factor in determining the fate of the universe is gravity. And to give you a little better idea of how these two fates are possible, let me give you a couple of examples to illustrate how they would work. If you toss a ball in the air, it will reach some maximum height where it stops momentarily and then returns to your hands. In this case the force of gravity is strong enough to brake and decelerate the moving ball to the point where it reverses its velocity. This is what the big crunch is like.
If, on the other hand, we launch a rocket into the far reaches of outer space, never to return, we have an example of the big chill. In this case, the rocket's energy of motion exceeds the gravitational energy, and the rocket continues on forever because the Earth's gravity was incapable of stopping the motion. So in both examples it's the amount of gravity that affects the outcome. But there are some other factors we need to look at besides gravity. One is the second law of thermodynamics and the other is the shape of the universe.
This second law is also linked to another physical process: entropy. Entropy is the measure of the amount of disorder in the universe. It reflects the concept that once something wears down it won't build itself back up without outside help. A broken egg will never reassemble itself. In a closed system, entropy never decreases, only increases or remains constant. So if the universe is a closed system, it will slowly run down and die. If on the other hand it is an open system, order can increase and entropy decrease, because there is input coming from somewhere else that will help bring this about.
Excerpted from The Complete Idiot's Guide to Theories of the Universe 2001 by Gary F. Moring. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.